This second correction is also a plus correction, subject to the same error as the first on account of the obliquity, its maximum value for an angle of 30° is about 6′, and is greatest in latitude 45°; for other latitudes, it is equal {6′ × sin(double the lat.)}/R. The three principal corrections for protuberance may be _estimated_ from the following table, calculated for every 15° of latitude for an angle of 30°, or when the correction is greatest. Latitude. 1st Corr. 2d Corr. 3d Corr. 0 + 20′ + 0 - 2 15 + 19 + 3 - 1.5 30 + 15 + 5 - 1.5 45 + 10 + 6 - 1. 60 + 5 + 5 - 1 70 + 1 + 3 - 0.5 We can now apply this correction to the latitude of the vortex just found: Latitude on the sphere 42° 45′ 38″ n. Correction for protuberance + 14 22 ---------- Correct latitude 43 00 00 MILWAUKIE STORM, JULY 2. As this example was calculated about ten days before the actual date, we have appended an extract from the Milwaukie papers, which is in the same longitude as Ottawa, in which place the calculation was made. It is needless to remark that the latitude of Milwaukie corresponds to the calculated latitude of the centre of the vortex. It is not intended, however, to convey the idea that the central line is always the most subject to the greatest violence--a storm may have several centres or nuclei of disturbance, which are frequently waning and reviving as the storm progresses. Generally speaking, however, the greatest action is developed along the line previously passed over by the axis of the vortex. "SUMMIT, Waukesha Co., Wis., July 4, 1853.